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Commit26c44e1

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Merge pull request#869 from henklaak/feature_print_zpk
Add zpk display option for transfer functions
2 parents177cba9 +6933973 commit26c44e1

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2 files changed

+238
-24
lines changed

2 files changed

+238
-24
lines changed

‎control/tests/xferfcn_test.py

Lines changed: 125 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -9,8 +9,9 @@
99

1010
importcontrolasct
1111
fromcontrolimportStateSpace,TransferFunction,rss,evalfr
12-
fromcontrolimportss,ss2tf,tf,tf2ss
13-
fromcontrolimportisctime,isdtime,sample_system,defaults
12+
fromcontrolimportss,ss2tf,tf,tf2ss,zpk
13+
fromcontrolimportisctime,isdtime,sample_system
14+
fromcontrolimportdefaults,reset_defaults,set_defaults
1415
fromcontrol.statespimport_convert_to_statespace
1516
fromcontrol.xferfcnimport_convert_to_transfer_function
1617
fromcontrol.tests.conftestimportslycotonly,matrixfilter
@@ -906,6 +907,128 @@ def test_printing_mimo(self):
906907
assertisinstance(str(sys),str)
907908
assertisinstance(sys._repr_latex_(),str)
908909

910+
@pytest.mark.parametrize(
911+
"zeros, poles, gain, output",
912+
[([0], [-1],1,
913+
'\n'
914+
' s\n'
915+
'-----\n'
916+
's + 1\n'),
917+
([-1], [-1],1,
918+
'\n'
919+
's + 1\n'
920+
'-----\n'
921+
's + 1\n'),
922+
([-1], [1],1,
923+
'\n'
924+
's + 1\n'
925+
'-----\n'
926+
's - 1\n'),
927+
([1], [-1],1,
928+
'\n'
929+
's - 1\n'
930+
'-----\n'
931+
's + 1\n'),
932+
([-1], [-1],2,
933+
'\n'
934+
'2 (s + 1)\n'
935+
'---------\n'
936+
' s + 1\n'),
937+
([-1], [-1],0,
938+
'\n'
939+
'0\n'
940+
'-\n'
941+
'1\n'),
942+
([-1], [1j,-1j],1,
943+
'\n'
944+
' s + 1\n'
945+
'-----------------\n'
946+
'(s - 1j) (s + 1j)\n'),
947+
([4j,-4j], [2j,-2j],2,
948+
'\n'
949+
'2 (s - 4j) (s + 4j)\n'
950+
'-------------------\n'
951+
' (s - 2j) (s + 2j)\n'),
952+
([1j,-1j], [-1,-4],2,
953+
'\n'
954+
'2 (s - 1j) (s + 1j)\n'
955+
'-------------------\n'
956+
' (s + 1) (s + 4)\n'),
957+
([1], [-1+1j,-1-1j],1,
958+
'\n'
959+
' s - 1\n'
960+
'-------------------------\n'
961+
'(s + (1-1j)) (s + (1+1j))\n'),
962+
([1], [1+1j,1-1j],1,
963+
'\n'
964+
' s - 1\n'
965+
'-------------------------\n'
966+
'(s - (1+1j)) (s - (1-1j))\n'),
967+
])
968+
deftest_printing_zpk(self,zeros,poles,gain,output):
969+
"""Test _tf_polynomial_to_string for constant systems"""
970+
G=zpk(zeros,poles,gain,display_format='zpk')
971+
res=str(G)
972+
assertres==output
973+
974+
@pytest.mark.parametrize(
975+
"zeros, poles, gain, format, output",
976+
[([1], [1+1j,1-1j],1,".2f",
977+
'\n'
978+
' 1.00\n'
979+
'-------------------------------------\n'
980+
'(s + (1.00-1.41j)) (s + (1.00+1.41j))\n'),
981+
([1], [1+1j,1-1j],1,".3f",
982+
'\n'
983+
' 1.000\n'
984+
'-----------------------------------------\n'
985+
'(s + (1.000-1.414j)) (s + (1.000+1.414j))\n'),
986+
([1], [1+1j,1-1j],1,".6g",
987+
'\n'
988+
' 1\n'
989+
'-------------------------------------\n'
990+
'(s + (1-1.41421j)) (s + (1+1.41421j))\n')
991+
])
992+
deftest_printing_zpk_format(self,zeros,poles,gain,format,output):
993+
"""Test _tf_polynomial_to_string for constant systems"""
994+
G=tf([1], [1,2,3],display_format='zpk')
995+
996+
set_defaults('xferfcn',floating_point_format=format)
997+
res=str(G)
998+
reset_defaults()
999+
1000+
assertres==output
1001+
1002+
@pytest.mark.parametrize(
1003+
"num, den, output",
1004+
[([[[11], [21]], [[12], [22]]],
1005+
[[[1,-3,2], [1,1,-6]], [[1,0,1], [1,-1,-20]]],
1006+
('\n'
1007+
'Input 1 to output 1:\n'
1008+
' 11\n'
1009+
'---------------\n'
1010+
'(s - 2) (s - 1)\n'
1011+
'\n'
1012+
'Input 1 to output 2:\n'
1013+
' 12\n'
1014+
'-----------------\n'
1015+
'(s - 1j) (s + 1j)\n'
1016+
'\n'
1017+
'Input 2 to output 1:\n'
1018+
' 21\n'
1019+
'---------------\n'
1020+
'(s - 2) (s + 3)\n'
1021+
'\n'
1022+
'Input 2 to output 2:\n'
1023+
' 22\n'
1024+
'---------------\n'
1025+
'(s - 5) (s + 4)\n'))])
1026+
deftest_printing_zpk_mimo(self,num,den,output):
1027+
"""Test _tf_polynomial_to_string for constant systems"""
1028+
G=tf(num,den,display_format='zpk')
1029+
res=str(G)
1030+
assertres==output
1031+
9091032
@slycotonly
9101033
deftest_size_mismatch(self):
9111034
"""Test size mismacht"""

‎control/xferfcn.py

Lines changed: 113 additions & 22 deletions
Original file line numberDiff line numberDiff line change
@@ -69,7 +69,14 @@
6969

7070

7171
# Define module default parameter values
72-
_xferfcn_defaults= {}
72+
_xferfcn_defaults= {
73+
'xferfcn.display_format':'poly',
74+
'xferfcn.floating_point_format':'.4g'
75+
}
76+
77+
def_float2str(value):
78+
_num_format=config.defaults.get('xferfcn.floating_point_format',':.4g')
79+
returnf"{value:{_num_format}}"
7380

7481

7582
classTransferFunction(LTI):
@@ -92,6 +99,10 @@ class TransferFunction(LTI):
9299
time, positive number is discrete time with specified
93100
sampling time, None indicates unspecified timebase (either
94101
continuous or discrete time).
102+
display_format: None, 'poly' or 'zpk'
103+
Set the display format used in printing the TransferFunction object.
104+
Default behavior is polynomial display and can be changed by
105+
changing config.defaults['xferfcn.display_format'].
95106
96107
Attributes
97108
----------
@@ -198,6 +209,17 @@ def __init__(self, *args, **kwargs):
198209
#
199210
# Process keyword arguments
200211
#
212+
# During module init, TransferFunction.s and TransferFunction.z
213+
# get initialized when defaults are not fully initialized yet.
214+
# Use 'poly' in these cases.
215+
216+
self.display_format=kwargs.pop(
217+
'display_format',
218+
config.defaults.get('xferfcn.display_format','poly'))
219+
220+
ifself.display_formatnotin ('poly','zpk'):
221+
raiseValueError("display_format must be 'poly' or 'zpk',"
222+
" got '%s'"%self.display_format)
201223

202224
# Determine if the transfer function is static (needed for dt)
203225
static=True
@@ -432,22 +454,29 @@ def _truncatecoeff(self):
432454
[self.num,self.den]=data
433455

434456
def__str__(self,var=None):
435-
"""String representation of the transfer function."""
457+
"""String representation of the transfer function.
436458
437-
mimo=self.ninputs>1orself.noutputs>1
459+
Based on the display_format property, the output will be formatted as
460+
either polynomials or in zpk form.
461+
"""
462+
mimo=notself.issiso()
438463
ifvarisNone:
439-
# TODO: replace with standard calls to lti functions
440-
var='s'ifself.dtisNoneorself.dt==0else'z'
464+
var='s'ifself.isctime()else'z'
441465
outstr=""
442466

443-
foriinrange(self.ninputs):
444-
forjinrange(self.noutputs):
467+
forniinrange(self.ninputs):
468+
fornoinrange(self.noutputs):
445469
ifmimo:
446-
outstr+="\nInput %i to output %i:"% (i+1,j+1)
470+
outstr+="\nInput %i to output %i:"% (ni+1,no+1)
447471

448472
# Convert the numerator and denominator polynomials to strings.
449-
numstr=_tf_polynomial_to_string(self.num[j][i],var=var)
450-
denstr=_tf_polynomial_to_string(self.den[j][i],var=var)
473+
ifself.display_format=='poly':
474+
numstr=_tf_polynomial_to_string(self.num[no][ni],var=var)
475+
denstr=_tf_polynomial_to_string(self.den[no][ni],var=var)
476+
elifself.display_format=='zpk':
477+
z,p,k=tf2zpk(self.num[no][ni],self.den[no][ni])
478+
numstr=_tf_factorized_polynomial_to_string(z,gain=k,var=var)
479+
denstr=_tf_factorized_polynomial_to_string(p,var=var)
451480

452481
# Figure out the length of the separating line
453482
dashcount=max(len(numstr),len(denstr))
@@ -461,10 +490,9 @@ def __str__(self, var=None):
461490

462491
outstr+="\n"+numstr+"\n"+dashes+"\n"+denstr+"\n"
463492

464-
# See if this is a discrete time system with specific sampling time
465-
ifnot (self.dtisNone)andtype(self.dt)!=boolandself.dt>0:
466-
# TODO: replace with standard calls to lti functions
467-
outstr+="\ndt = "+self.dt.__str__()+"\n"
493+
# If this is a strict discrete time system, print the sampling time
494+
iftype(self.dt)!=boolandself.isdtime(strict=True):
495+
outstr+="\ndt = "+str(self.dt)+"\n"
468496

469497
returnoutstr
470498

@@ -485,7 +513,7 @@ def __repr__(self):
485513
def_repr_latex_(self,var=None):
486514
"""LaTeX representation of transfer function, for Jupyter notebook"""
487515

488-
mimo=self.ninputs>1orself.noutputs>1
516+
mimo=notself.issiso()
489517

490518
ifvarisNone:
491519
# ! TODO: replace with standard calls to lti functions
@@ -496,18 +524,23 @@ def _repr_latex_(self, var=None):
496524
ifmimo:
497525
out.append(r"\begin{bmatrix}")
498526

499-
foriinrange(self.noutputs):
500-
forjinrange(self.ninputs):
527+
fornoinrange(self.noutputs):
528+
forniinrange(self.ninputs):
501529
# Convert the numerator and denominator polynomials to strings.
502-
numstr=_tf_polynomial_to_string(self.num[i][j],var=var)
503-
denstr=_tf_polynomial_to_string(self.den[i][j],var=var)
530+
ifself.display_format=='poly':
531+
numstr=_tf_polynomial_to_string(self.num[no][ni],var=var)
532+
denstr=_tf_polynomial_to_string(self.den[no][ni],var=var)
533+
elifself.display_format=='zpk':
534+
z,p,k=tf2zpk(self.num[no][ni],self.den[no][ni])
535+
numstr=_tf_factorized_polynomial_to_string(z,gain=k,var=var)
536+
denstr=_tf_factorized_polynomial_to_string(p,var=var)
504537

505538
numstr=_tf_string_to_latex(numstr,var=var)
506539
denstr=_tf_string_to_latex(denstr,var=var)
507540

508541
out+= [r"\frac{",numstr,"}{",denstr,"}"]
509542

510-
ifmimoandj<self.noutputs-1:
543+
ifmimoandni<self.ninputs-1:
511544
out.append("&")
512545

513546
ifmimo:
@@ -1285,7 +1318,7 @@ def _tf_polynomial_to_string(coeffs, var='s'):
12851318
N=len(coeffs)-1
12861319

12871320
forkinrange(len(coeffs)):
1288-
coefstr='%.4g'%abs(coeffs[k])
1321+
coefstr=_float2str(abs(coeffs[k]))
12891322
power= (N-k)
12901323
ifpower==0:
12911324
ifcoefstr!='0':
@@ -1323,6 +1356,48 @@ def _tf_polynomial_to_string(coeffs, var='s'):
13231356
returnthestr
13241357

13251358

1359+
def_tf_factorized_polynomial_to_string(roots,gain=1,var='s'):
1360+
"""Convert a factorized polynomial to a string"""
1361+
1362+
ifroots.size==0:
1363+
return_float2str(gain)
1364+
1365+
factors= []
1366+
forrootinsorted(roots,reverse=True):
1367+
ifnp.isreal(root):
1368+
ifroot==0:
1369+
factor=f"{var}"
1370+
factors.append(factor)
1371+
elifroot>0:
1372+
factor=f"{var} -{_float2str(np.abs(root))}"
1373+
factors.append(factor)
1374+
else:
1375+
factor=f"{var} +{_float2str(np.abs(root))}"
1376+
factors.append(factor)
1377+
elifnp.isreal(root*1j):
1378+
ifroot.imag>0:
1379+
factor=f"{var} -{_float2str(np.abs(root))}j"
1380+
factors.append(factor)
1381+
else:
1382+
factor=f"{var} +{_float2str(np.abs(root))}j"
1383+
factors.append(factor)
1384+
else:
1385+
ifroot.real>0:
1386+
factor=f"{var} - ({_float2str(root)})"
1387+
factors.append(factor)
1388+
else:
1389+
factor=f"{var} + ({_float2str(-root)})"
1390+
factors.append(factor)
1391+
1392+
multiplier=''
1393+
ifround(gain,4)!=1.0:
1394+
multiplier=_float2str(gain)+" "
1395+
1396+
iflen(factors)>1ormultiplier:
1397+
factors= [f"({factor})"forfactorinfactors]
1398+
1399+
returnmultiplier+" ".join(factors)
1400+
13261401
def_tf_string_to_latex(thestr,var='s'):
13271402
""" make sure to superscript all digits in a polynomial string
13281403
and convert float coefficients in scientific notation
@@ -1486,6 +1561,10 @@ def tf(*args, **kwargs):
14861561
Polynomial coefficients of the numerator
14871562
den: array_like, or list of list of array_like
14881563
Polynomial coefficients of the denominator
1564+
display_format: None, 'poly' or 'zpk'
1565+
Set the display format used in printing the TransferFunction object.
1566+
Default behavior is polynomial display and can be changed by
1567+
changing config.defaults['xferfcn.display_format']..
14891568
14901569
Returns
14911570
-------
@@ -1538,7 +1617,7 @@ def tf(*args, **kwargs):
15381617
15391618
>>> # Create a variable 's' to allow algebra operations for SISO systems
15401619
>>> s = tf('s')
1541-
>>> G = (s + 1)/(s**2 + 2*s + 1)
1620+
>>> G = (s + 1) /(s**2 + 2*s + 1)
15421621
15431622
>>> # Convert a StateSpace to a TransferFunction object.
15441623
>>> sys_ss = ss("1. -2; 3. -4", "5.; 7", "6. 8", "9.")
@@ -1609,12 +1688,24 @@ def zpk(zeros, poles, gain, *args, **kwargs):
16091688
name : string, optional
16101689
System name (used for specifying signals). If unspecified, a generic
16111690
name <sys[id]> is generated with a unique integer id.
1691+
display_format: None, 'poly' or 'zpk'
1692+
Set the display format used in printing the TransferFunction object.
1693+
Default behavior is polynomial display and can be changed by
1694+
changing config.defaults['xferfcn.display_format'].
16121695
16131696
Returns
16141697
-------
16151698
out: :class:`TransferFunction`
16161699
Transfer function with given zeros, poles, and gain.
16171700
1701+
Examples
1702+
--------
1703+
>>> from control import tf
1704+
>>> G = zpk([1],[2, 3], gain=1, display_format='zpk')
1705+
>>> G
1706+
s - 1
1707+
---------------
1708+
(s - 2) (s - 3)
16181709
"""
16191710
num,den=zpk2tf(zeros,poles,gain)
16201711
returnTransferFunction(num,den,*args,**kwargs)

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